Recently, with the rapid development of rail transit, safety issues of rail transit vehicles during operation have received increasing attention. Meanwhile, the operation of rail transit is an large system in which electrical service, maintenance, vehicles, signals, embarkation service and the like are integrated. In this case, occasional human errors or mechanical failures are inevitable. Thus, train collision accidents occur over time, and result in tremendous casualties and property losses. The most effective method for reducing the impact of a collision accident is improving the crashworthiness of a vehicle.
Currently, when designing the crashworthiness of a rail vehicle, unmanned areas at both ends of the vehicle are generally designed with weak stiffness and manned areas are designed with strong stiffness, so that the unmanned areas undergo a large plastic deformation during an collision accident of the vehicle to dissipate the collision energy, while the manned areas merely undergo an elastic deformation or small plastic deformation, thereby ensuring the space integrity of the manned areas.
There are two type of structure of the unmanned area for dissipating energy: a load-bearing energy absorbing structure and a dedicated energy absorption structure. In addition to the function of absorbing collision energy during a vehicle collision accident, the load-bearing energy absorption structure also bears loads in normal applications. The characteristics of this structure at least lie in that it provides a low cost and a simple construction, but needs cumbersome repairs and a high repair cost after collision. The dedicated energy absorption structure is mounted on either ends of a vehicle and bears no load in normal applications. These structures dissipate collision energy through plastic deformation thereof only when collision accident of the vehicle occurs. The dedicated energy absorption structure is widely used in the crashworthiness design of modern rail vehicles due to its stable deformation, convenient replacement, and low repair cost, etc.
Dedicated collision energy absorption structures can be known from the following related art documents.
Patent application CN 102398558 relates to a collision buffering energy absorption device, a base plate of the collision buffering energy absorption device is connected to a guide boss, and keep a certain distance away from a friction guide plate; an energy absorption tube with an axial groove surrounds around the guide boss; and a substrate is mounted at the other end of the energy absorption tube. The groove may be machined in the outer surface of the energy absorption tube or in the inner surface of the energy absorption tube, and the energy absorption tube may be partially torn at the groove or not torn during assembling. When the substrate is pressed, the substrate drives the energy absorption tube to move toward the base plate, during the moving, a portion of energy is absorbed through the friction between the energy absorption tube and the guide boss; meanwhile, due to the cross-sectional area of the guide boss becomes larger as the guide boss approaches the base plate, the energy absorption tube is torn at the axial groove at a certain moment, and a portion of the energy is absorbed during tearing; then the torn part of the energy absorption tube is bent to enter a space between the friction guide plate and the base plate, and during the advancing stroke of the torn part, a portion of the energy is absorbed through friction; and eventually the buffering energy absorption effect is achieved. This collision buffering energy absorption device is simple in structure, easy to manufacture, and low in cost. Meanwhile, this collision buffering energy absorption device may absorb energy load uniformly, has high capacity, and can serve as good passive safety protection equipment.
Additionally, patent CN 103148144 also disclosed a novel energy absorption device buffering uniformly. The energy absorption device comprises a round pre-torn tube, a guide friction round tube and a punch. The round pre-torn tube is a thin-walled metal round tube, and one end of the tube is circular truncated cone in shape and is in the form of a funnel, this end is provided with a cone angle; the other end of the tube, with the guide friction round tube, are fixed on a same panel by adhesive or brazing and are kept coaxial relative to each other. The guide friction round tube is slightly longer than the round pre-torn tube in length, in order for the energy absorption device partially cooperates with the punch before the energy absorption device is impacted. A tearing slot is provided in the wall of the round pre-torn tube and a tearing opening is provided in an end of the round pre-torn tube. The head of the punch is in the form of a circular truncated cone, and the transition between the head and the end of the round pre-torn tube closed to the punch is steady and smooth. A through hole interference fitted with the outer wall of the guide friction round tube is provided in the punch and plays a role of axial positioning and absorbing a portion of energy through friction. This device absorbs energy mainly by the bulging resulting from the extruding of the punch into the round pre-torn tube and the following tear of the round tube. Specifically, the round pre-torn tube has an inner diameter between 30 and 80 mm, a wall thickness h1 between 2 and 5 mm, and a length L1 between 60 and 120 mm. Compared with the conventional energy absorption modes, the tear and curling damage of the round tube is more effective in energy absorption effect than breaking, axial flection or turnover, and the device has the characteristics of long effective stroke and smooth impact force.
However, due to the dedicated energy absorption structures disclosed in the above documents, only an crushing energy absorption manner of a thin-walled structure can be employed, and there may be a significant impact force peek in the structure of this type at the time of initial crushing, which would increase the damage to subsequent structures, and cause significant inconvenience to the crashworthiness design of the structure. Furthermore, the maximum effective stroke of the crushing energy absorption manner of the thin-walled structure is generally less than 70%, and thus this structure cannot fully utilize the effective stroke of the energy absorption device.